While there are clearly some reliability problems with the AC86, you only hear about the ones that fail. There are still plenty of them out there working just fine. I think as long as you have a warranty,
@Tech9 's advice is sound: since you don't need an AX router just yet, use the AC86 for the warranty period and if/when it dies, then see what's the top router at that time. Or if the 68 still works (with the new antenna) you might not need anything at all? It's your call, but there is always a newer "latest greatest" coming out
FWIW, I have 2x AC86 (HW Rev R1.5, 2018) and they are still going strong. Temp is around 77C, ambient ~23C. When one dies I'll swap in an AX86, until then I'm good.